The 205K distributor’s advance is operated by a single vacuum. A tube on the vacuum canister is connected to a metal vacuum tube by a short length of vacuum hose. At the other end of the metal tube it is connected also by a short length of vacuum hose to the driver’s side brass vacuum inlet of the 30 Pict-1 (VW 105-1) Carburetor.
The metal tube is configured with a loop (like a large upside-down letter U) at the top at the vacuum port of the carburetor. This is to discourage any gasoline residual from being aspirated into the vacuum canister.
Here’s a little history of the evolution of the metal vacuum tube.
Into December, 1961, only a braided hose connected the vacuum canister directly to the carburetor. This was remedied during the month of December, 1961, with a kit supplied by or installed by VW dealerships. This kit was unusual in that a metal tube, formed into a loop as a complete circle, was connected by a 40mm length of braided hose to the carburetor vacuum tube and, at the bottom end, by a 40mm length of braided hose to the vac canister. This was to be a permanent installation.
VW installed a circular loop with one long end (to the vac canister) and one short end. (to the carburetor)
As well, there was a “service installation” which was a metal tube formed into a complete circle-loop which was an abbreviated version of the above metal tube. This tube was short on either end. It was to be installed on previous years as a replacement for cars which were fitted only with the braided hose. 40mm was cut from the existing braided hose and the metal tube-loop was inserted between the longer end and the 40mm piece.